a) Field of the Invention
The invention is directed to an arrangement for pressure compensation for optical devices, particularly spectrometers or the like optical devices, for compensating pressure differences caused by changes in temperature and air pressure between the internal pressure and the external pressure at a housing of an optical device enclosing optical units.
b) Description of the Related Art
In general, there is a risk of impairing the performance of the optical units with their functional surfaces in that these surfaces can be contaminated by solid or liquid particles of substances in air through contact of the optical functional surfaces with normal air, which can lead to an impairment or total failure of the operation of the optical units of an optical device. However, when a transfer of air to the optically active functional surface is required for optical reasons, these optical units are installed with their functional surfaces in the housing of the optical device in a sealed manner. On the one hand, this prevents soiling of the optical functional surfaces, but on the other hand the disadvantage of this procedure consists in that pressure differences between the internal pressure and the surrounding pressure of the housing can occur due to changes in temperature and air pressure, so that the tightness of the housing of the optical device is highly stressed.
Therefore, there are strict requirements for the sealing elements of a housing of an optical device with optical units contained therein. On the one hand, absolutely tight housings are difficult to achieve and, on the other side, these strict requirements for the sealing elements of the housing result in increased technical and monetary expenditure on manufacturing.
Devices for pressure compensation are known from the prior art for other technical areas. For example, DE 198 50 561 A1 shows a device for pressure compensation in a hydraulic system, particularly for a clutch or a brake in a motor vehicle. In this device, a volume compensating element which communicates with the pressure compensating space and which increases its volume by a predetermined extent when there is a vacuum in the pressure space is provided in an embodiment form as a flexible diaphragm.
Further, a gear unit, particularly a planetary gear unit, is known from DE 199 40 235 C1, in which the pressure balance between the interior of the gear unit housing and the outer surroundings is carried out while simultaneously preventing the escape of impurities in that a deformable diaphragm arranged in the pressure compensating chamber is provided for the interior of the shaft or a gear unit part connected to this shaft, which diaphragm divides the external surroundings from the interior of the gear unit.
DE 198 59 272 A1 discloses another form of a device for pressure compensation in which an interior space in a container being transported is closed by means of a pressure compensating insert which is fixedly connected to a protective foil liner for pressure compensation in this interior space. A pressure potential occurring in the protective foil liner is conducted to the pressure compensation device of the transport container by a diaphragm valve which is integrated in the cover of the pressure compensating insert. In these technical solutions, the diaphragm performs the function of a volume compensating element.